We will study the physicochemical properties of various lymphokines and attempt to isolate them in a high state of purity in order to perform definitive studies on their mechanisms of action and on their roles in cellular immune phenomena in vivo as well as in vitro. Most of the work will be done with guinea pig lymphokines. Our long-term objective is to develop fundamental chemical and biological information in order to promote better understanding of the roles of various lymphokines in infectious disease, in diseases of autoimmune origin, in allergic disorders, and in transplantation and tumor immunity. The following near-term investigations are projected: (1) Attempted isolation of lymphotoxin and production of an antiserum against the purified material. (2) Studies of the role of lymphotoxin in direct lymphocyte-mediated cytotoxicity in vitro. (3) Studies of the physicochemical properties of mitogenic factor. (4) Attempted isolation of mitogenic factor and production of an antiserum against the purified material. (5) Studies of the possible role of mitogenic factor in facilitating antibody formation and of its possible role in non- specifically stimulating the production of other lymphokines. Studies of the chemical and biological properties of other lymphokines will be initiated as interested students and fellows become available.